This invention relates generally to analog memories.
Usually, semiconductor non-volatile memories store digital data in the form of either a 1 or a 0, or as 00, 01, 10, 11. Thus, each memory cell may store one to four digital states or 2 bits of information.
However, information to be stored may be in the form of smoothly varying analog information. Analog information may include the characteristics of a non-periodic wave such as a sound wave. In order to digitize this information, a large number of samples are taken at various slices of time. Information corresponding to each sample may be taken as time slices along the time domain of the signal. For each slice the amplitude or average amplitude during that slice of time may be digitized into n bits (usually 8 or more bits). As a result, a number of digital bits may be needed to record the information for each time slice.
As an alternative, analog information may be stored in an analog memory capable of storing the magnitude as an analog value instead of as a digitized value. In one case, a range of levels for the memory cells corresponds to a range of analog values. Storing the analog value for each time slice in each memory locations instead of the digitized value as a number of bits stored in several bit locations can reduce the cost of storage.
In view of the large amount of analog information that may need to be stored, it would be desirable to have an analog memory that is able to efficiently store this information. Examples of storable analog information include audio and video information, radio signals, and other wireless signals.
Thus, there is a need for better ways to provide analog memories.